Hot rolled SA335 P91 Chrome Moly High Pressure Seamless steel boiler pipe

Product Details

Alloy Steel Pipe A335 Gr. P5, P9, P11, P22, P91

Learn about the alloy steel pipes specification ASTM A335 that covers “chrome-moly” seamless pipes with remarkable resistance to corrosion and good tensile strength at high-temperature service. Generally, ASTM A335 P11, P22, and P91 pipes are used in power generation and in downstream oil and gas, P5 and P9 grades are for refinery applications.

ALLOY PIPE A335

How to define alloy pipes?

Alloy pipes are tubular with higher percentages, than standard carbon steel pipes, of alloying elements as Molybdenum (Mo), Chromium (Cr), Nickel, etc. Actually, the ASTM A335 covers “low-alloy” steel pipes, i.e. pipes that have a total amount of alloying elements below 5%. The addition of higher percentages of alloying elements (example Nickel and Chromium) transforms the steel into higher alloys, like stainless steel, duplex, up to super-alloyed materials like Inconel, Hastelloy, Monel, etc.

Alloy steel pipes are used in the energy industry for high temperature and very low-temperature service (cryogenic), or for applications with very high pressures.

ASTM A335 alloy steel pipes fit ASTM A234 WPx series buttweld fittings (WP5, WP9, WP91) and A182 Fx forged fittings and flanges (A182 F5, F9, F11, F22, F91). All these materials have similar chemical and mechanical properties and can be joined or welded.

Alloying elements

The addition of Molybdenum (“Moly”) increases the strength of the steel and its elastic limit, enhance the steel resistance to wear, its impact qualities, and the hardenability. It also improves the resistance to softening, makes chromium steel less prone to embrittlement and prevents pitting.

Chromium, a key element also for stainless steel alloys, prevents steel oxidation at elevated temperatures and increases the resistance of steel to corrosion. It enhances the tensile, yield, and hardness properties of low-alloy pipes at room temperatures.

Other alloying elements, present in various degrees in pipes of all grades are:

Aluminum: decreases oxygen from steelmaking

Boron: used to produce fine grain size and enhance steel hardness

Cobalt: used to enhance the steel’s heat and wear-resistance

Manganese: gives better steel hardenability

Nickel: Enhances toughness, hardenability and impact strength at low temperatures

Silicon: decreases oxygen, enhances hardenability and toughness

Titanium: prevents precipitation of chromium carbide

Tungsten: refines steel grain size and enhance the steel hardness, especially at high temperatures

Vanadium: gives steel enhanced fatigue resistance

As mentioned, low-alloy steels have a total amount of alloying elements below 5%; high alloy steel has a higher percentage of these elements.

A335 PROPERTIES

CHEMICAL COMPOSITION

The types of alloy steel covered by the ASTM A335 – ASME SA335 specification are designed with a “P” prefix, from P5 to P92. Grades P11/P22 and P91/92 are typically found in power stations, whereas grade P5 and P9 are more common for application in the petrochemical industry. Grades P9, P91 are, in the list, the more expensive.